Detailed Message:

TF271001: An error occurred while attempting to send an e-mail notification to the following address: email id. Further e-mail notification errors that occur within the next five minutes might not be logged. Verify that the e-mail notification settings are correct in the Team Foundation Administration Console.
Exception Message: Service not available, closing transmission channel. The server response was: 4.4.1 Connection timed out (type SmtpException)

Error :

TFS Email Notifications Delayed or Not Sent

Explanation:

I started experiencing problems with TFS alert notification mails. TFS Email Notifications were Delayed or Not received. The TFS alert notification was working fine for the past 2 years.

Solution:

Following are the investigation done to fix the notification problem

1. Verified the SMTP server and found out no problems with it. (Anonymous sender was enabled in Exchange for tfs@domain.com)
2. Verified whether "Visual Studio Team Foundation Background Job Agent" service is running in TFS App tier. Service was running fine. (Restarted the service too)

3. I ran the follwoing query to find tfs job failures in the tbl_JobHistory table in the Tfs_Configuration database

SELECT TOP 10 DATEADD(hour, -7, StartTime) as StartTimePDT, Result, ResultMessage
FROM [Tfs_Configuration].[dbo].[tbl_JobHistory] WHERE JobId = 'A4804DCF-4BB6-4109-B61C-E59C2E8A9FF7' AND Result <> 0
ORDER BY StartTime DESC

Note: The JobId GUID for the “Team Foundation Server Event Processing” job with the namespace: “Microsoft.TeamFoundation.JobService.Extensions.Core.NotificationJobExtension” is 'A4804DCF-4BB6-4109-B61C-E59C2E8A9FF7'

Query result:

"There were errors or warnings during notification delivery.    35573/35598 emails delivered.  0/0 soap notifications delivered.   25 errors.  0 warnings.    Set /Service/Integration/Settings/NotificationJobLogLevel in the TF registry to 2 to see errors and warnings"   

4. Queried [dbo].[tbl_EventNotification] table in the [Tfs_DefaultCollection] database to see for failures.

SELECT * FROM [Tfs_DefaultCollection].[dbo].[tbl_EventNotification]

Found many records with failed status.

5. Deleted all records with failed status

Delete FROM [Tfs_DefaultCollection].[dbo].[tbl_EventNotification] where [status] = 'failed'

Note : I dint see any harm in deleting all the records from FROM [Tfs_DefaultCollection].[dbo].[tbl_EventNotification]

Delete FROM [Tfs_DefaultCollection].[dbo].[tbl_EventNotification]

6. Queried [dbo].[tbl_EventNotification] table in the [Tfs_DefaultCollection] database to see the notification event backlogs count.

SELECT * FROM [Tfs_DefaultCollection].[dbo].[tbl_ClientEvent]

Found around 1000 pending events that need to be processed.

7. Deleted all pending events backlogs

Delete FROM [Tfs_DefaultCollection].[dbo].[tbl_ClientEvent] 

Verified the fix by trigging the new alerts, All the alerts got processed and also received the notification mails.

link to turn on verbose log

link to Decrease or Increase notification delay settings in TFS

Explanation:

By default notification delay is set to 120 seconds. The notifications are processed in batchs for every 2 minutes. The notification delay can be set in the TF registry
Note: The TFS registry mentioned is not the Windows Registry on the TFS server.

Solution:

The registry value can be changed using the PowerShell script or using the TfsReg tool

Following is the command to set the notification delay to 1 minute using the tool:

tfsreg.exe /server:http://tfs:8080/tfs /path:/Service/Integration/Settings/NotificationJobDelay /value:60

Note: Restart the TFS IIS app pool for the change to take effect.

Exception:

mt.exe : general error c101008d: Failed to write the updated manifest to the resource of file "XXXXXX.exe". Access is denied.

Explanation:

The error may occur in some situations due to a race condition between the compiler process and the anti-virus file-system auto-protect.

Workaround:

 Disable deferred file scanning by adding a registry key.

1. Click Start > Run 

2. Type in: regedit and click OK

3. Navigate to: 

"HKEY_LOCAL_MACHINE\SOFTWARE\Symantec\Symantec Endpoint Protection\AV\Storages\Filesystem\RealTimeScan" (32 bit Operating System) or

“HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Symantec\Symantec Endpoint Protection\AV\Storages\Filesystem\RealTimeScan” (64 bit Operating System)

4. Click Edit > New > DWORD Value

5. Name the new value: DeferredScanning

6. Open DeferredScanning

7. In the Value data field add “0” (1 = on, 0 = off)

8. Click OK

9. Close the Registry Editor window.

Reference 

Solution:

I uninstalled a software named "Sendori".  The error got disappeared.

Discussion about Sendori

http://answers.microsoft.com/en-us/protect/forum/protect_other-protect_scanning

Explanation:

The default threshold is set to 30 seconds, The warning occurs when the threshold exceeds.

Log Name:      Application
Source:        TFS Services
Date:          1/27/2013 8:53:37 AM
Event ID:      7006
Task Category: None
Level:         Warning
Detailed Message: There are no active requests for service host DefaultCollection that exceed the warning threshold of 30.
 
Log Name:      Application
Source:        TFS Services
Date:          1/27/2013 8:52:22 AM
Event ID:      7005
Task Category: None
Level:         Warning
Detailed Message: A request for service host DefaultCollection has been executing for 37 seconds, exceeding the warning threshold of 30.

Solution:

Increase the threshold limit, if you experience performance issues due to these warnings. execute the following SQL statements

use [<Collection DB name>]

DECLARE @registryUpdates typ_KeyValuePairStringTableNullable
INSERT @registryUpdates ([Key], [Value])
SELECT '#\Configuration\ServiceHostMonitor\TotalExecutionElapsedThreshold\', '300'
 
EXEC prc_UpdateRegistry 1, 'Test', @registryUpdates, 1